The present invention relates to improvements in or to flat type gas burners, particularly for a domestic appliance. The gas burner comprises a burner body provided with a cylindrical vertical, axial gas inlet passage which shields a gas injector, and a cap covering the burner body and resting on the latter through an annular crown provided with flame orifices distributed circumferentially. The annular surface of the burner body bordering the outlet of the inlet passage for the gaseous mixture and the opposite surface of the cap are frustoconic to define an annular convergent-divergent system extending approximately across the gas jet. The burner body and the crown define, in addition, between their opposite surfaces, an annular decompression chamber situated between the abovesaid convergent-divergent system and the flame orifices.
The present trend in the field of furnishing kitchens is, more and more, towards completely built-in electrical home appliances. That is, the appliances are supported against a wall and enclosed between two neighboring pieces of furniture and/or equipment of substantially the same height.
This trend also affects gas cookers, with the result that there no longer exists any possible air flow around the appliance or within the latter, around the oven and to the outside. The only opening directed outwardly remains the chimney for removing combustion products from the oven and, as the case may be, from the grill.
When, in equipment thus installed, the oven door is manipulated a little too rapidly, there occurs in the oven an over-pressure on the closing of the door or an under-pressure on opening the door. The only route for the passage of air for reequilibrating the air pressure in the oven remains the chimney of the oven. However, the cross-section of the latter is determined exactly to stabilize a correct temperature in the oven and in general it is insufficient to deliver by itself the air flow necessary for reequilibrating the internal pressure. Consequently, the air movement takes place, at least partly, through the orifices for supplying the oven with fresh air. These orifices open into the inner space of the oven between the sides and top walls of the appliance. Now, it is also in this inner space that there are situated the apertures for taking in primary air for the burners. These apertures are supported immediately above the burners, on the upper wall forming the stove top. As a result, the pressure variation due to the actuation of the door of the oven is transmitted right into the burners. Whatever the type of burner equipping the stove, this pressure variation of the air in the very heart of the burner is prejudicial to the stability of the flames. There is even a risk of it becoming dangerous, by reason of the liability to extinction of the burners when operating at idling rate.
In particular, in the case of flat type burners, the configuration of these burners results in there not being a sufficient expansion volume, between the convergent-divergent system and the flame orifices, to damp a sudden pressure variation of the air. In this case, there exists a real risk of extinction of the flames, either by blowing out the flames (over-pressure of the air generated on the closing of the oven door), or by aspiration of the flames (under-pressure of the air caused on the opening of the door of the oven).